Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $69.27   11.108%   $76.9645   $76.96   $76.95   $77.00  
  Purchase #2 $246.29   5.302%   $259.3483   $259.35   $259.35   $259.30  
  Purchase #3 $214.55   13.792%   $244.1407   $244.14   $244.15   $244.10  
  Purchase #4 $152.41   4.529%   $159.3126   $159.31   $159.30   $159.30  
  Purchase #5 $167.26   4.492%   $174.7733   $174.77   $174.75   $174.80  
  Purchase #6 $93.85   13.348%   $106.3771   $106.38   $106.40   $106.40  
  Purchase #7 $145.93   11.529%   $162.7543   $162.75   $162.75   $162.80  
  7 purchase totals = $1,089.56       $1,183.6708   $1,183.66   $1,183.65   $1,183.70